How to get rid of this virus on PC?

[Ross]

Every time I visit certain social media websites, I get these annoying pop up ads on the side of the page and every time I navigate and visit other pages, these annoying pop ups always persist. This hasn't happened before only recently has this become an issue. I run Norton Antivirus and initiate a full system scan, but once it's finished the results say that everything is okay. I'm assuming it's not malware or spyware installed, but adware. How can I get rid of this? Please and thank you!